I've just (15th February 2011) had to set this up again for someone on an Ubuntu 10.10 box.

And to my speechless amazement (16th February 2011), it worked absolutely the same way on Radek Ostrowski (a complete stranger) 's mac at dev8d, thus condemning him to years of suffering at the hands of Aquamacs.

This method is still my favourite, still the one I actually use in practice, and still the easiest, and it's been stable for about a year now.

Since I've just confirmed that it still works, I've moved it back to the top.

Install maven:

$sudo apt-get install maven2

Then create a pom.xml file to tell maven which repositories to use. There's an example below to copy and paste.

Once you've got maven installed, and made a pom.xml file, then:

$mvn clojure:repl

Will start a REPL with clojure 1.2 and clojure-contrib 1.2 on the classpath. The REPL should use jLine to give it editing and history on all platforms.

If you like to use EMACS instead, then

$mvn clojure:swank

Will start a swank server, which you can connect to with M-x slime-connect.

That's it from the clojure side.

To set up emacs, and equip it to talk to the clojure swank server:

$sudo apt-get install emacs

Then install the emacs lisp package archive (see http://tromey.com/elpa/) by evaluating this code:

(cut and paste it into the scratch buffer, put the cursor in the middle, and use M-C-x):

Now use M-x package-list-packages to bring up the list of packages, and use i and then x to mark and then install slime, slime-repl, and clojure-mode.

Then connect emacs to the already running clojure image with M-x slime-connect

That should be it. You should now be at a running clojure 1.2 repl inside emacs.

Here's an example of a pom.xml file that pulls in clojure and clojure-contrib 1.2 . Just cut and paste it.

As well as the essentials, I've also added: the clojars.org repository, where many useful clojure packages live; the maven versions plugin, which helps with keeping everything cutting edge; and jline so that command line repls work better (mvn clojure:repl)

I like to have my startup repls conditioned a little, so if you have a startup script that you always want to run, add this snippet

<configuration>

<replScript>startup.clj</replScript>

</configuration>

to the clojure-maven-plugin section so that when maven starts a repl, the code in startup.clj is loaded as the first action. This is a good place to set print-length and print-level, so that they will be set before the swank server starts, which means that you won't hang emacs by evaluating an infinite sequence.

I also like to require everything on the classpath, so that I can use things like find-doc to find out about everything.

pom.xml files look terrifying, but they're really not. It's just that xml is such a godawful verbose way to write things out.

It contains: the addresses of three repositories which hold vital code; the names and versions of four vital jar files that you need; and the names and versions of two helpful maven plugins.